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-
- QuickSat Satellite Prediction Program
- Version 2.15L July 11, 2004
-
-
- Description of the Documentation
-
- This documentation consists of the following parts:
-
- 1. Introduction line 20
- 2. Operation of the program line 84
- 3. How to run the test line 143
- 4. Description of the control file line 159
- 5. Description of the intrinsic magnitudes file(s) line 592
- 6. Description of the orbital elements file(s) line 685
- 7. Description of the prediction output line 723
-
-
-
- Introduction
-
- This program has gradually evolved over many years. Its purpose has always
- been to support visual observations of satellites. For that reason, the
- normal execution of the program produces a single prediction for each
- satellite. That prediction point is the culmination point if that point is
- outside the Earth's shadow. Otherwise, a point outside the Earth's shadow
- that is nearest the culmination point is chosen. Multiple predictions for
- each satellite may also be chosen. The prediction of an object's magnitude
- is a primary goal. The probable error in time of prediction is computed by
- a heuristic. The observer may create his own "intrinsic magnitudes override"
- file so that his own information will "override" the information in the
- default "intrinsic magnitudes" file. There is a "radio" predictions flag
- that will bypass all of the parts of the program having to do with magnitudes,
- the Earth's shadow, RA and Dec.
-
- This program is freeware. There are no restrictions on its distribution.
-
- The program is written in Fortran. This version requires the use of a
- coprocessor. This is a "DOS" program.
-
- The program has certain "built-in" limits: 1) No more than 2500 names and
- magnitudes may be stored from the "intrinsic magnitudes" file. 2) If the
- "store elements in memory" option is chosen, no more than 2000 element sets
- may be stored from the orbital elements files. 3) No more than 400 different
- set of "size" values can be stored. The program requires an IBM compatible
- computer. The program uses about 450K bytes of memory.
-
- The following files are provided:
- 1. QUICKSAT.DOC - this file
- 2. QUICKSAT.EXE - the executable
- 3. QUICKSAT.MAG - a file of intrinsic magnitudes, sizes, and RCS values
- 4. QUICKSAT.CTL - an input test control file
- 5. QUICKSAT.DAT - an input test elements file (these elsets are 11 years old)
- 6. QUICKSAT.REF - the output file from the test
- 7. ADDCR.EXE - a program to add CR characters to a file
-
- The author of the program is Mike McCants. I can be reached at
- "mmccants@ev1.net" on the Internet. The current version of Quicksat is
- located in my ftp area, which can be accessed from my home page.
- (http://users2.ev1.net/~mmccants/) I can make a Unix version for Sun
- Solaris workstations and I have a Linux version on my home page.
-
- Changes for version 2.15L: When the culmination prediction is inside
- or too close to the Earth's shadow, a value of 1/2 the step size is
- used to search for a prediction that is outside the Earth's shadow.
- This may result is a prediction instead of no prediction for the
- previous algorithm or it may result in prediction(s) that are higher
- in the sky (and closer to the Earth's shadow entry/exit). A slightly
- more accurate prediction is generated for the time for a culmination
- prediction for an object with very high drag.
-
- Change for version 2.15K: The "Time Error" output value is in seconds.
- If the value is less than 4, it is left blank.
-
- Change for version 2.15J: The Microsoft Fortran compiler version 5.0
- is now being used. The previous versions used an older Microsoft
- compiler and the latest version of Windows XP would not execute the
- program because of a very strange way that the executable was generated
- by that compiler. I have not generated version that does not require
- a co-processor.
-
-
-
- Operation of the Program
-
-
- The user is expected to operate the program in the following way:
-
- I. Input data preparation
- 1. Orbital elements are obtained. Note: the elements file must have
- a carriage return character at the end of each line. If you obtain
- a file from kilroy.jpl.nasa.gov/pub/elements and you fail to add
- a carriage return character to the end of each line, the message
- "no elements were loaded" will be printed. The program ADDCR can
- be used with the command "ADDCR input-file output-file".
- 2. Optionally, names, intrinsic magnitude, sizes, or comments
- can be added to an "intrinsic magnitudes override" file.
-
- II. Control file preparation
- 1. The control file is edited to specify either "tonight" or the year,
- month and day (or zero) for the time of predictions, the latitude
- and longitude for the observing site, and the name(s) of the satellite
- elements input file(s).
-
- III. Program execution
- 1. The program is executed. (This is a DOS program.)
- 2. The name of the control file to be used can be placed on the command
- line as a single parameter. If no control file is specified on the
- command line and there is a control file named QUICKSAT.CTL in the
- current directory, then that file is used. If there is not a file
- named QUICKSAT.CTL in the current directory, the program prompts for
- the name of the control file to be used.
- 3. As determined by the control file, the user may be requested for the
- day of the month for the desired predictions.
- 4. As determined by the control file, the user may be requested to enter
- up to 20 NCAT numbers of objects to be predicted for.
- 5. As determined by the control file, the user may be requested for the
- name of the file to contain output.
- 6. As determined by the control file, the user may be requested for the
- name of a file containing orbital elements.
-
- IV. After the program completes, the output file may then be printed or
- displayed.
-
- The program operates in the following way:
-
- 1. The control file is read.
- 2. The intrinsic magnitudes data is read into memory.
- (Note: the program will continue even if this file is not present.)
- 3. The intrinsic magnitudes override data is read into memory.
- 4. The orbital elements are read into memory (if the "store elements
- in memory" flag is true).
- 5. All predictions for the first night are generated and stored in memory.
- 6. The predictions are sorted into time order and written to the output file.
- Steps 5 and 6 are repeated for subsequent days.
-
- However, if a "combine" operation is specified, predictions for only one night
- should be specified and steps 1, 4, and 5 are repeated for each set of control
- lines. Then step 6 is performed.
-
-
-
- How to Run the Test
-
-
- 1. Enter QUICKSAT to execute the program.
-
- 2. Compare the generated file, OUTPUT.TXT to the reference file, QUICKSAT.REF.
-
- Note: Of course, lower case file names may be used, upper case is shown here
- for clarity.
-
- Note: the elements in the QUICKSAT.DAT test file are from 1990 and the
- test output is for 1990. You must obtain current elements in order to
- compute current predictions.
-
-
-
- Description of the Control File
-
-
- This file controls the operation of the program. If the name of a control
- file is entered on the command line, that file is processed. If no filename
- parameter is given and a control file named QUICKSAT.CTL exists in the
- current directory, it will be used. If not, the user will be prompted to
- enter the name of the control file to be used.
-
- There are at least 21 lines in this file. Each will be described in turn.
-
- NOTE: Each line is in a "free form" format. Values may be separated by
- spaces or a comma. Comments may be placed after the data values.
-
- NOTE: Two or more complete sets of control information may be "combined"
- so that a single output file will contain output generated by any of them.
-
- Example test input control file (QUICKSAT.CTL):
-
- 1990 7 Year, month number
- 26 0 Start date, end date
- -0.3 -5.5 Start time, end time, "A" flag
- 30.3340 97.7600 520. 5105 Crestway Dr.
- -5 CDT 12 correction for UT to time zone, time zone name, 12/24 flag
- 2000 Epoch of predicted RA, Dec
- 6.5 Magnitude limit
- 15 Altitude cut-off value
- 1.0 The search/step parameter value
- T True means store all elements in memory (limit 2000)
- T True means accept only the most recent elements for each object
- F True means ignore shadow test
- T 1 True means generate multiple prediction points, how many each way
- T True means output distance values in miles
- T True means generate a blank line before each object's prediction.
- Up to 10 non-blank flags to select class(es) of objects
- A Output format flag, R/P option, D/C/N option, Azimuth option
- quicksat.mag Intrinsic magnitudes input file
- none Intrinsic magnitudes override file
- output.txt Output file
- quicksat.dat Elements input file
- EOF End of input file list
-
-
- Line 1: This line is either the word "tonight" or the year and
- month number.
-
- tonight Use current computer date
- 1990 7 Year, month number
-
- If the word "tonight" appears in lower case, then the current computer
- date will be used to obtain the year, month, and day. In this case,
- line 2 must NOT be present in the control file. Note: the computer time
- is ignored. If it is 1AM on the 18th, predictions will be generated
- for the evening of the 18th and/or the morning of the 19th, not for the
- morning of the 18th.
-
-
- Line 2: This line gives the dates for prediction.
-
- 26 0 Start date, end date
-
- Note: if line 1 has the word "tonight", line 2 must NOT be present.
-
- The first number is first day for predictions, the second number is the
- last day for predictions. An end date of zero means perform predictions
- for only one day. If the start date is specified as zero, the user will
- be prompted and asked to supply the start date and stop date from the
- terminal. If only one number is entered, predictions for only that day
- will be performed.
-
- NOTE: Due to the way the date is used in the program, the user must NORMALLY
- enter the date which ENDS at midnight. In the test case, the number 26 is
- given as the date. This means that predictions will be performed for the
- evening of July 26 and the morning of July 27. July 26 was a Thursday. The
- title, "July 26 Thu evening", will appear at the top of the predictions.
- The user should ALWAYS double check to make sure that a one day error is
- not being made.
-
- If it is desired to run predictions for only the morning of July 27, then
- the date must STILL be entered as 26. The start time, end time values
- should be changed to +5.5, +0.3 to run morning predictions only.
-
- Note: This is NOT the case if the "A" flag is set or the "radio" predictions
- flag is set. In these cases, the actual UT date must be entered.
-
-
- Line 3: This line specifies the prediction time limits and the "A" flag.
-
- -0.3 -5.5 Start time, end time, "A" flag
-
- The prediction time limits values are in hours. A negative number means
- "before", a positive number means "after". Unless "absolute" mode or "radio"
- predictions mode has been specified, the reference times are the times that
- the sun is 10 degrees below the observer's horizon. Therefore a value of
- -0.3 means begin predictions 18 minutes BEFORE the time that the sun is 10
- degrees below the observer's horizon in the EVENING. A value of -5.5 means
- end the predictions at the time which is 5 hours 30 minutes BEFORE the time
- the sun is 10 degrees below the observer's horizon in the MORNING. These
- 10 degree reference times are printed as part of the output title.
-
- To run evening predictions, a span of 0 to -6 is appropriate. To run morning
- predictions, a span of +6 to 0 is appropriate. A span of 0 to 0 runs
- predictions for both morning and evening. But, of course, the "-6" value
- depends greatly on the latitude and time of year.
-
- If the start/stop times are followed by the letter "A", then absolute times
- (UT) are specified.
-
- If The "A" flag or "radio" predictions have been specified, then these times
- are relative to zero hours UT. That is, -5.0 +2.0 would be a 7 hour span
- beginning 5 hours before 0 hours UT and ending 2 hours after 0 hours UT.
- Remember, in these cases, the start date is the actual UT date.
-
-
- Line 4: This line gives the latitude, longitude, height, and site name
- of the observer.
-
- 30.334 97.760 520. 5105 Crestway Dr.
-
- The site name text can be up to 24 characters in length.
- The longitude is positive for WEST longitude, negative for east longitude.
- Note that this is the opposite from most prediction programs.
- Height is in feet.
-
-
- Line 5: This line gives the UT correction value, the time zone name,
- and the 12/24 hour flag.
-
- -5 CDT 12 Correction for UT to time zone, time zone name, 12/24 flag
-
- The time zone correction value is added to the UT time of prediction to
- produce a local time of prediction. If the resulting value is zero or
- negative, 24 will be added to make it greater than zero. If the resulting
- value is greater than or equal to 24, then 24 will be subtracted. In
- either case, the date will be adjusted. The result is a time from 0 to 23.
- The designation AM or PM is based on this value.
-
- If the 12/24 flag is not 12, then this result is the output. If the flag
- is 12, then the time value is adjusted to be from 1 to 12.
-
-
- Line 6: This line gives the epoch of the RA and Dec values.
-
- 2000 Epoch of RA, Dec
-
-
- Line 7: This line gives the "cut-off" magnitude.
-
- 6.5 Magnitude limit
-
- Any prediction whose magnitude is fainter than the "cut-off" magnitude
- will be suppressed. If the intrinsic magnitude of an object is unknown
- but an RCS value is known, then an intrinsic magnitude for the object will
- be computed from the RCS value for use by this "cut-off" test. If the
- RCS value is unknown, then the intrinsic magnitude is assumed to be either
- 4.0 or 7.0 for this magnitude limit test. For objects whose NORAD catalog
- number is less than or equal to the "7.0 test value", an intrinsic magnitude
- of 7.0 is assumed. For objects with a greater number, 4.0 is assumed.
-
-
- Line 8: This line gives the altitude "cut-off" value.
-
- 15 Altitude cut-off value
-
- Any prediction which has an altitude below this "cut-off" value will be
- suppressed.
-
-
- Line 9: This line gives the search/step parameter value.
-
- 1.0 The search/step parameter value
-
- This parameter value is used as a "step size" value in two situations.
- If multiple points of prediction are specified, this value gives the step
- size between each. If the culmination point is inside the Earth's shadow,
- then 1/2 of this value is used as the step size to search for a point that
- is outside of the Earth's shadow.
-
- If multiple points of prediction are specified, this parameter should be
- adjusted to provide the desired spacing between the points. A value of 1.0
- will give the following results: For an object at 400 miles, about a 1
- minute spacing. For an object at 600 miles, about a 1:30 spacing. For an
- object at 1000 miles, about a 2 minute spacing. If an object will pass
- through the observer's zenith, then a step size of 1.0 will give predictions
- at an altitude of about 50 degrees before and after the zenith prediction.
-
- If multiple points of prediction are not specified, 1/2 of the value is
- used to search for a position that is about 20 miles outside of the Earth's
- shadow. Thus a smaller search size value would require more computation,
- but would often find a point higher in the sky that has a shadow height
- of more than 20 miles.
-
-
- Line 10: This line gives the "store elements in memory" flag.
-
- T True means store all elements in memory (limit 2000)
-
- If this flag is true, elements are read from the input file(s) and
- stored in memory. No more than 2000 elements may be stored. The
- "keep only the most recent elements" flag works across files.
-
- If this flag is false, elements are read in and processed, so there is
- no limit on the number of elements that can be processed. However,
- the "keep only the most recent elements" works only when the multiple
- element sets for an object are grouped together in an element file.
- If the elements for an object are not together in the file or appear
- in multiple files, then multiple predictions will be generated.
-
-
- Line 11: This line gives the "keep only the most recent elements" flag.
-
- T True means keep only the most recent elements for each object
-
- If this flag is false, all elements in all input files will be accepted
- for predictions. If there are duplicate element sets for an object, then
- there will be multiple predictions for that object. If this flag is true,
- each element set will be checked to see if it is for the same object as an
- element set already read in. If so, then the element set which has the
- older epoch will be discarded. Thus only the latest data for each object
- will remain for prediction purposes. But, see limitations on this process
- described under line 10.
-
-
- Line 12: This line gives the shadow test flag.
-
- F True means ignore shadow test
-
- If this flag is false, no prediction will be generated for any point
- where the height of the object is less than about 20 miles above the
- Earth's shadow. If this flag is true, such prediction points will not be
- suppressed, so predictions inside the Earth's shadow will be generated.
- Such predictions will have negative shadow height values.
-
-
- Line 13: This line has the multiple points flag (T/F) and the limit on
- the number of points that will be generated.
-
- T 1 True means generate multiple prediction points, how many each way
-
- If this flag is false, only one prediction point will be generated for each
- pass of each object. If this flag is true, multiple points may be generated.
- Each point must satisfy the shadow test, altitude cut-off, and magnitude
- cut-off. The time difference between the points is determined by the step
- size parameter value and the object's mean height. The number of points
- is the limit on how many points can be generated "on each side" of the
- culmination prediction. In the normal case, a value of 1 will generate
- 3 prediction points - the culmination point and one point both before and
- after it. However, if the culmination point is in the Earth's shadow, then
- only one point will be generated. Similarly, a value of 2 would normally
- generate 5 points, but could generate only 1 or 2.
-
- Note: a value of 99 means "no limit".
-
- Note: the step size parameter is the value on line 9.
-
-
- Line 14: This line specifies the miles/kilometers flag.
-
- T True means output distance values in miles
-
-
- Line 15: This line specifies the blank line flag.
-
- T True means generate a blank line before each object's prediction.
-
-
- Line 16: This line specifies flags for "classes" of objects.
- Or specific NCAT numbers may be entered from the terminal.
- Or alt/azi or RA/dec output limits may be specified.
-
- 1. Classes of objects
-
- f t s Up to 10 non-blank flags to select class(es) of objects
-
- If there are no classes specified, then all objects will be predicted for.
- If there are non-blank characters for the classes, then only those objects
- which have one of these characters as their "flag" value will be predicted
- for. In general, "c" means a classified object, "f" or "t" means a tumbling
- object whose tumble period is of interest, and "s" means an object that is
- now steady (but has tumbled in the past). (See the definition of the flag
- value in the intrinsic magnitudes file description.)
-
- 2. Specific objects
-
- If the word "prompt" (in lower case) appears in the first 6 columns, then
- the prompt "Enter next NCAT number" will be given. A single NCAT number
- can be entered. If the entered value is non-zero, then the prompt will be
- repeated. If a blank or zero is entered, then predictions will be generated
- for just the objects specified. Up to 20 NCAT numbers may be entered.
-
- 3. Limits for a "box"
-
- If the letters "AA" are given in columns 1 and 2, then alt/azi output limits
- are read from the next line. The format for this line is:
-
- all alh azl azh alt low lim, alt high, azi low, azi high in degrees
-
- The four values, altitude lower limit, altitude upper limit, azimuth lower
- limit, and azimuth upper limit are in degrees. Only predictions which
- are inside this "box" will be generated. Note: the limits 340 and 20
- could be specified for a box around azimuth 0.
-
- Note: all other limits are still in effect. In particular, the altitude
- limit (line 8) is still in effect. The magnitude limit and the Earth's
- shadow are still in effect.
-
- Note: it is normally advisable to lower the step size parameter to a "small"
- value (line 8) and increase the number of steps (line 13) so that one or
- more predictions for an object going through the box will be generated.
-
- If the letters "RD" are given in columns 1 and 2, then RA/dec output limits
- are read from the next line. The format for this line is:
-
- rhl rml rhh rmh dcl dch RA hrs low, RA mns low, RA hr/mn high, dec low, high
-
- The six values, RA hours/minutes low limit, high limit, dec low limit, and
- dec high limit must be specified. Only predictions which are inside this
- "box" will be generated. The values 23 40 and 0 20 could be used to specify
- a box around 0 hours RA. See notes for AA option above.
-
-
- Line 17: This line specifies the output format and options.
-
- 12345678901
- A Output format flag, R/P option, D/C/N option, azimuth option,
- Range Limit option
-
- The standard output format is A. Each set of predictions for an object is
- preceded by a title line containing the name, sizes, intrinsic magnitude, and
- comments. Format D is the same as A except that azimuth is followed by
- elevation. The alternate formats B and C are "one-line" formats where the
- name appears on the same line as the prediction. These formats are described
- below. The format letter must be in upper case. If the format is A or D and
- a D appears in column 5, then the object designation will be printed after the
- satellite name. (The designation comes from the intrinsic magnitudes file.)
-
- If the output format is B or C, then column 3 may contain the letter P indi-
- cating that the phase angle is to be printed instead of the range. If column
- 5 contains the letter N, then the comments information will not be printed.
-
- If the output format is R, then "radio" predictions will be generated. There
- is no output of magnitude, shadow height, RA, or Dec.
-
- If column 7 contains the letter A, then the azimuth will be adjusted by 180
- degrees so that 0 means south, 90 means west, and 180 means north.
-
- If columns 9-10 contain the letters RL, then the range limit value is
- specified on the next line. The range limit is in miles if the miles
- flag is true and in kilometers if the miles flag is false. Any prediction
- with a range greater than the specified value will be discarded.
-
- Note: the format flag may be in column 1 or 2, the R/P flag may be in
- column 3 or 4, the D/C/N flag may be in column 5 or 6, the azimuth
- option flag may be in column 7 or 8, and the range limit flag may be
- in columns 9-10 or 10-11. All letters must be upper case.
-
-
- Line 18: This line specifies the intrinsic magnitudes input filename.
-
- quicksat.mag Intrinsic magnitudes input file
-
- This file contains information on the name and intrinsic magnitude of
- objects. Comments may be retrieved for display with any prediction.
- The physical size may also be included. If this file is not found,
- a message will be printed and no such data will be available.
- (See further description below.) The filename must be in columns 1-40.
-
-
- Line 19: This line specifies the intrinsic magnitudes override filename.
-
- none Intrinsic magnitudes override file
-
- This file contains information that will "override" or supplement the
- information in the quicksat.mag file. The format is the same as the
- quicksat.mag file. The NCAT number is required. Other fields are
- optional. Any non-blank field will override the corresponding field
- in the quicksat.mag field. If there is no entry in the quicksat.mag
- file for this object, this entry will be used. (See the intrinsic
- magnitude file description below.) The filename must be in columns 1-40.
-
-
- Line 20: This line specifies the output filename.
-
- output.txt Output file
-
- The name of the output file may be specified. Alternatively, the
- keyword "prompt" may be specified (in lower case). In this case, a
- prompt message is issued at the terminal and the user must enter the
- output filename.
-
-
- Line 21: This line specifies the first orbital elements filename.
-
- quicksat.dat Elements input file
-
- The name of the first elements file may be specified. Alternatively,
- the keyword "prompt" may be specified (in lower case). In this case, a
- prompt message is issued at the terminal and the user may enter a simgle
- elements filename.
-
- The elements file must contain elements in standard "2-line" element form.
- Preceding each set of elements, an optional object name may appear. The
- name will be obtained from columns 1-14. This name will only be used if
- there is no entry for the object in the intrinsic magnitudes file.
-
- 2-line elements are recognized by the digits 1 or 2 in column 1 followed by
- a blank space. Any lines which do not match this format will be ignored.
-
- Note: Any element set with a mean motion less than 4.0 will be ignored.
- A separate program (HighFly) is available in my ftp area for generating
- predictions for these objects.
-
- Note: If the elements file does not have proper DOS CR/LF characters at
- the end of each line, no elsets will be recognized. If there are no CR
- characters at the end of each line, the program ADDCR may be used to add them.
-
- If the keyword "prompt" is NOT present on line 21, then additional input
- files may be specified on subsequent lines. Normally the "T" flag on line
- 11 would be used to tell the program to keep only the most recent element
- set for each object. The end of the input file list is specified by either
- the physical end of the control file or a line which contains "end" or "EOF".
-
- No more than 10 input files may be specified.
-
- If the keyword "combine" is present, then a complete new set of control lines
- follows this keyword and the output file will contain the combined results.
- Each set of control lines should specify the same site location and the
- same (single) day for prediction output. Each should agree in the type of
- output that will be generated. The intrinsic magnitudes file and the
- intrinsic magnitudes override file will not be processed.
-
-
-
- Description of the Intrinsic Magnitudes File
-
-
- This file contains information about satellites. Each line contains the
- NORAD catalog number, the designation, class, name, size, RCS value and
- comments. A line could be up to 87 characters in length.
-
- The format for the "name" part of the line is:
-
- 1 2 3
- 1234567890123456789012345678901234567
- catno f desig... name.......... mag.
- 00005 58 B2 Vanguard 1 9.0
-
- Columns 1-5 contain the NORAD catalog number.
-
- Column 7 contains either a "code" letter or the "class" letter of the object.
- The following code letters are used: "d" means that the object has decayed
- or returned. "h" means that the object is in a high altitude orbit. The
- class letter "c" means the object has a classified orbit. The class letters
- "f" and "t" indicate that the object is of interest because it is tumbling.
- The class letter "s" indicates that the object has tumbled in the past, but
- is currently steady. Objects with a "d", "h", or "g" are not stored in memory
- by Quicksat.
-
- Columns 9-16 contain the designation. This information is saved and printed
- when the A output format is chosen and the D flag appears in column 6 of
- line 16.
-
- Columns 19-32 contain the satellite name.
-
- Columns 34-37 contain the intrinsic magnitude, which is defined to be the
- maximum apparent brightness of the satellite when it is seen at full phase
- at a range of 1000 kilometers. The program will adjust this value according
- to the actual circumstances of the prediction to determine a maximum possible
- apparent magnitude. Of course many cylindrical objects are often one or two
- magnitudes fainter than this predicted magnitude when their actual orientation
- is unfavorable on a particular pass.
-
-
- The format for the "size" part of the line is:
-
- 4 5
- 901234567890
- 7.4 2.4 0.0
-
- The three numbers are the size values. Many of the values given in this
- file were obtained from data posted to the Canadian Space Society BBS by
- Ted Molczan. He normally obtains these values from the RAE Tables. I have
- "adjusted" some of the values to bring the computed intrinsic magnitude into
- better agreement with my observations. Some sizes have been obtained from
- Joel Runes' catalog.
-
- If there is only one value, the object is assumed to be a sphere and the
- value is its diameter in meters. If there are two values, the object is
- assumed to be a cylinder - the first value is its length and the second
- value is its diameter. If there are three values, then the object is
- assumed to be rectangular and the values are for its three sides.
-
-
- The format for the "RCS" part of the line is:
-
- 5
- 1234
- 6.4
-
- The RCS (Radar Cross Section) value is the "median" of all of the "different"
- values that appeared in the Satellite Situation Reports from about 5 years
- ago to the present. The RCS value is in square meters, so it should be
- closely related to the size values for the object.
-
-
- The format for the "comments" part of the line is:
-
- 5 6 7 8
- 67890123456789012345678901234567
- observational information
-
- Columns 56-87 contain the observational comments. These comments will be
- printed above each prediction with the name or after the first line of each
- prediction when "one-line" output is specified (unless the "N" flag is set).
-
- The quicksat.mag file may have the following comments:
- 1. date: per nn (dec) - the tumble period in seconds (was decreasing)
- 3. var n - the object is sometimes fainter than its maximum brightness
- by the specified value (in magnitudes).
- 4. fl nn - the object sometimes "flashes" and increases brightness
- by the specified amount.
- 5. fl to nnn - the object has be observed to "flash" up to the given
- magnitude.
-
-
-
- Description of the Orbital Elements File(s)
-
-
- An orbital elements input file must be in the form of NORAD two-line
- elements. Each may be preceded by the satellite name. Any line that does
- not have a "1" or "2" in column 1 and a blank in column 2 will be ignored.
-
- Examples of two-line elements:
-
- Alouette 1
- 1 00424U 62B-A 1 90192.70736421 .00000170 00000-0 19423-3 0 3322
- 2 00424 80.4633 261.8991 0022426 207.0003 152.9977 13.67365462386044
- ATS 3
- 1 03029U 67111 A 90194.54223643 -.00000074 00000-0 99999-4 0 3953
- 2 03029 13.2438 21.0153 0013818 204.7992 155.1757 1.00272749 83052
- Cosmos 398
- 1 04966U 71 16 A 90200.49713217 .00042980 17752-4 27181-3 0 9862
- 2 04966 51.5262 157.4892 2249896 208.4414 137.3099 11.10705110595285
-
- The name field is read, but is only used when no entry appears in the
- intrinsic magnitudes file.
-
- Note that only 14 characters of a name field will be remembered. This
- means that there is a chance that an object and its rocket body may
- have the "same" name if the first 14 characters are the same.
-
- Note: There is no attempt to check the "check-digit" value.
-
- Note: The drag term which appears after the epoch is used. The change in
- the drag term value is not used. The Bstar term is not used.
-
- Note: The ATS object is discarded because its mean motion is less than 4.
-
- Note: If carriage return characters are not present at the end of each line,
- the program ADDCR may be used to add them.
-
-
-
- Description of the Prediction Output
-
-
- The first line is an "echo" of some of the input values from
- the control file:
-
- 30.334 97.760 520. 5105 Crestway Dr. 2000 6.5 15 F F T T T
-
- The latitude, longitude, height, and site name are listed. The epoch
- of RA and Dec is given. The magnitude cut-off and altitude cut-off
- are given. Five true/false flags are given.
-
-
- The next line gives the date and time zone:
-
- *** 1990 July 26 Thu evening *** Times are PM CDT *** 2116 558
-
- For the prediction date of July 26, the evening predictions are for
- Thursday. The predictions times are PM for the time zone CDT. The
- value 2116 is the local time of twilight when the sun is 10 degrees below
- the horizon. The value 558 is the local time of morning twilight when
- the sun is 10 degrees below the horizon.
-
-
- --- The following describes the "A" two-line output format information ---
-
- The next line gives the titles for each data line:
-
- H M S Tim Al Azi C Dir Mag Dys F Hgt Shd Rng EW Phs R A Dec
-
- Each of these fields will be discussed below.
-
-
- The object header line is given before the predictions for each object:
-
- 20625 Cosmos 2082 Rk 10.4 3.9 23 2.0
-
- The NORAD catalog number is given. The name is given. The three size
- values, and the RCS value are given if they are available. The class
- value is given. The observed intrinsic magnitude is given (if available).
- Finally, the comments field from the intrinsic magnitudes file is given.
-
- Each set of predictions has the following form:
-
- H M S Tim Al Azi C Dir Mag Dys F Hgt Shd Rng EW Phs R A Dec
- 9 41 54 18 36 261 66 4.0 31 4 536 493 830 .9 115 1251 10.7
- 9 43 22 18 41 297 C 92 3.9 31 4 536 499 759 1.0 123 1234 38.7
- 9 44 49 18 34 331 117 4.3 31 4 537 505 856 1.0 124 1140 64.8
-
- The time is UT unless a time zone was specified in the input file.
- In the current example, -5 was given to convert UT to CDT.
-
- The Tim value is the estimated uncertainty in the time of prediction
- (in seconds). So, 18 seconds is a "likely" error in this prediction.
- If the time error is less than or equal to 3 seconds, then the field
- is left blank.
-
- The Al value is the altitude of the prediction point.
- The Azi value is the azimuth of the prediction point.
- The letter C after the azimuth indicates that this is the point of
- culmination. The absence of the C would indicate that this is not a
- culmination prediction.
-
- The Dir value is the direction that the satellite is traveling. A value
- of 0 means traveling "up". A value of 90 means "right". A value of 180
- means "down". A value of 270 means "left". In the given example, the
- satellite travels right and a little up from the southwest until the
- culmination point is reached. Then it travels right and a little down
- as it moves into the northwest.
-
- The Mag value is the predicted maximum magnitude if an observed intrinsic
- magnitude was avaliable. This does not mean that the satellite cannot be
- brighter or fainter than this magnitude. The satellite can be brighter
- if it reflects the sun better than expected at this phase angle. It can
- be fainter than expected if it reflects the sun worse than expected at this
- phase angle or if it is a non-spherical object and its particular orientation
- is unfavorable on this pass. Since the comment "var 2.5" appears, then it
- is likely that the object can change in brightness from this "maximum
- predicted magnitude" to a brightness that is 2.5 magnitudes fainter. Often
- such a variation will take place in less than 2 minutes. If "var att"
- appears, then the object varies very slowly and is usually constant at
- some brightness equal to or less than the prediction. However, the comment
- "var att" applies to a large percent of all objects, so I do not normally
- explicitly include this as a comment.
-
- If an observed intrinsic magnitude is not available, then the special value
- "20" is used for the intrinsic magnitude. This will normally produce a
- predicted magnitude between 18 and 24. If the observer has an expection of
- the intrinsic brightness because of a knowledge of the expected size, then
- this "20" magnitude can be transformed as follows: 20 is subtracted and the
- expected intrinsic magnitude is added. For example, if 20.4 appears, but
- the observer expects an intrinsic magnitude of 3.5, then 20.4 - 20 + 3.5 =
- 3.9 and the expected magnitude is 3.9. If the object is observed to be
- about 4.4, then an intrinsic magnitude of 4.0 would be appropriate.
-
- H M S Tim Al Azi C Dir Mag Dys F Hgt Shd Rng EW Phs R A Dec
- 9 41 54 18 36 261 66 4.0 31 4 536 493 830 .9 115 1251 10.7
- 9 43 22 18 41 297 C 92 3.9 31 4 536 499 759 1.0 123 1234 38.7
- 9 44 49 18 34 331 117 4.3 31 4 537 505 856 1.0 124 1140 64.8
-
- The Dys value is the number of days from the epch of the elements to the
- prediction date.
-
- The F value is the fraction of a revoltion (in tenths) that the object has
- made since its last perigee. A fractional value of 9, 0, or 1 indicates
- that the object is near perigee. A fractional value of 4, 5, or 6 indicates
- that the object is near apogee. A value of 2 indicates the object is rising
- from perigee to apogee.
-
- The Hgt value is the height of the object in miles or kilometers.
-
- The Shd value is the height of the object above the Earth's shadow.
-
- The Rng value is the range of the object.
-
- The EW value is the distance east/west that the orbital plane moves in
- one minute. If this satellite is one minute early, it will be 1.0 degrees
- to the east of the predicted position. If it is one minute late, it will
- be 1.0 degrees west of the predicted position.
-
- The Phs value is the sun-object-observer angle. A value of 0 indicates
- full phase, a value of 180 indicates new phase.
-
- The R A value is the right ascension of the prediction.
-
- The Dec value is the declination of the prediction.
-
-
- ---- The following describes the "B" output format information -----
-
- The NORAD catalog number, EW displacement/minute and phase angle are not
- displayed. The object name is given on the first output line only. If
- there is any comment information, it is given only after the first line.
-
- H M S Tim Azi ElC Dir Mag Dys F Hgt Shd Rng R A Dec RCS Name
- 9 41 54 18 261 36 67 4.0 31 4 536 493 830 1251 10.7 23 pCosmos 2082 Rk
- var 2.5
- 9 43 22 18 297 41C 92 3.9 31 4 536 499 759 1234 38.7
- 9 44 49 18 331 34 117 4.3 31 4 537 505 856 1140 64.8
-
- But if the "P" format flag is present, the phase angle is displayed instead
- of the range. If the "N" flag is present, any comments are suppressed.
-
-
- ---- The following describes the "C" output format information -----
-
- The "C" format is the same as the "B" format except that the altitude
- precedes the azimuth and the title says "Al Azi".
-
-
- ---- The following describes the "Radio" output format information -----
-
- H M S Tim Al Azi C Dys F Hgt Rng
- 20625 Cosmos 2082 Rk
- 9 41 54 18 36 261 31 4 536 830
- 9 43 22 18 41 297 C 31 4 536 759
- 9 44 49 18 34 331 31 4 537 856
-